Covert DateTime format from UTC to Local time by JavaScript

1. Upload the JavaScript file in Style Library and Published.
2. Register this uploaded JavaScript in the Master Page.
3. Call the DateTime format function like below:

 dateFormat(new Date(item.ArticleStartDate), 'mm/dd/yyyy')

4. Please find the JavaScript as below: (Copy and Past the Note pad and save as "date.format.js")

var dateFormat = function () {

var token = /d{1,4}|m{1,4}|yy(?:yy)?|([HhMsTt])\1?|[LloSZ]|"[^"]*"|'[^']*'/g,

timezone = /\b(?:[PMCEA][SDP]T|(?:Pacific|Mountain|Central|Eastern|Atlantic) (?:Standard|Daylight|Prevailing) Time|(?:GMT|UTC)(?:[-+]\d{4})?)\b/g,

timezoneClip = /[^-+\dA-Z]/g,

pad = function (val, len) {

val = String(val);

len = len || 2;

while (val.length < len) val = "0" + val;

return val;

};

// Regexes and supporting functions are cached through closure

return function (date, mask, utc) {

var dF = dateFormat;

// You can't provide utc if you skip other args (use the "UTC:" mask prefix)

if (arguments.length == 1 && Object.prototype.toString.call(date) == "[object String]" && !/\d/.test(date)) {

mask = date;

date = undefined;

}

// Passing date through Date applies Date.parse, if necessary

date = date ? new Date(date) : new Date;

if (isNaN(date)) throw SyntaxError("invalid date");

mask = String(dF.masks[mask] || mask || dF.masks["default"]);

// Allow setting the utc argument via the mask

if (mask.slice(0, 4) == "UTC:") {

mask = mask.slice(4);

utc = true;

}

var _ = utc ? "getUTC" : "get",

d = date[_ + "Date"](),

D = date[_ + "Day"](),

m = date[_ + "Month"](),

y = date[_ + "FullYear"](),

H = date[_ + "Hours"](),

M = date[_ + "Minutes"](),

s = date[_ + "Seconds"](),

L = date[_ + "Milliseconds"](),

o = utc ? 0 : date.getTimezoneOffset(),

flags = {

d:    d,

dd:   pad(d),

ddd:  dF.i18n.dayNames[D],

dddd: dF.i18n.dayNames[D + 7],

m:    m + 1,

mm:   pad(m + 1),

mmm:  dF.i18n.monthNames[m],

mmmm: dF.i18n.monthNames[m + 12],

yy:   String(y).slice(2),

yyyy: y,

h:    H % 12 || 12,

hh:   pad(H % 12 || 12),

H:    H,

HH:   pad(H),

M:    M,

MM:   pad(M),

s:    s,

ss:   pad(s),

l:    pad(L, 3),

L:    pad(L > 99 ? Math.round(L / 10) : L),

t:    H < 12 ? "a"  : "p",

tt:   H < 12 ? "am" : "pm",

T:    H < 12 ? "A"  : "P",

TT:   H < 12 ? "AM" : "PM",

Z:    utc ? "UTC" : (String(date).match(timezone) || [""]).pop().replace(timezoneClip, ""),

o:    (o > 0 ? "-" : "+") + pad(Math.floor(Math.abs(o) / 60) * 100 + Math.abs(o) % 60, 4),

S:    ["th", "st", "nd", "rd"][d % 10 > 3 ? 0 : (d % 100 - d % 10 != 10) * d % 10]

};

return mask.replace(token, function ($0) {

return $0 in flags ? flags[$0] : $0.slice(1, $0.length - 1); 

});

};

}();

// Some common format strings

dateFormat.masks = {

"default":      "ddd mmm dd yyyy HH:MM:ss",

shortDate:      "m/d/yy",

mediumDate:     "mmm d, yyyy",

longDate:       "mmmm d, yyyy",

fullDate:       "dddd, mmmm d, yyyy",

shortTime:      "h:MM TT",

mediumTime:     "h:MM:ss TT",

longTime:       "h:MM:ss TT Z",

isoDate:        "yyyy-mm-dd",

isoTime:        "HH:MM:ss",

isoDateTime:    "yyyy-mm-dd'T'HH:MM:ss",

isoUtcDateTime: "UTC:yyyy-mm-dd'T'HH:MM:ss'Z'"

};

// Internationalization strings

dateFormat.i18n = {

dayNames: [

"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat",

"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"

],

monthNames: [

"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec",

"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"

]

};

// For convenience...

Date.prototype.format = function (mask, utc) {

return dateFormat(this, mask, utc);

};